Why Zijinshan copper bioheapleaching plant works efficiently at low microbial activity – Study on leaching kinetics of copper sulfides and its implications

Zijinshan commercial bioheapleaching–SX–EW plant has been in operation since December 2005. 13.9 million tonnes of low grade copper sulfide ore (Cu 0.38%) has been leached efficiently with an annual recovery of 80% in this distinct leaching system with high iron concentration, high temperature, high acidity and low microbial activity. This paper is to study the key factors which influence the heap operation in Zijinshan. Dissolution kinetics of diginite and covellite was carried out in acid ferric sulfate solution under controlled redox potential. Moreover, column bioleaching tests were conducted in the laboratory with raffinate from the plant. Both results showed that the main factors accelerating dissolution rate of Cu1.8S/CuS were mainly temperature and ferric concentration, while redox potential only had a slight positive effect. The present work provides an insight into mineral kinetics to understand this unique bioheapleaching operation and gives further information for optimization of the existing practices.

► Fe3+ leaching of CuS/Cu1.8S is sensitive to temperature and [Fe3+], but not to Eh.
► High temperature favor bioleach of the ore despite low microorganism activity.
► A novel approach based on chemical kinetics is proposed to optimize bioheapleach.
► The possible leaching mechanism in Zijinshan bioheaps was proposed.